Method for manufacturing a segmented raised anode fluorescent symbol display tube

ABSTRACT

A method for securing display anodes to related support pins in a segmented planar raised anode fluorescent symbol display tube employing a weld and deweld procedure.

United States Patent Armstrong *Aug. 5, 1975 [5 METHOD FOR MANUFACTURINGA 156] References Cited SEGMENTED RAISED ANODE UNITED STATES PATENTSFLUORESCENT SYMBOL DISPLAY TUBE 3.666.91 1 5/1972 Armstrong 219/1 17[75] Inventor: James B. Armstrong, Phoenix, Ariz. 1 47 8/1972 Ruago313/1 8 R 3.7l6.899 2/1973 Kersletter et ul 1. 29/2514 [73] Assignee:Sperry Rand Corporation, New

York Primary Examiner-Roy Lake Notice; The porticm of the t f thiAssistant Examiner-James W. Davie patent subsequent to May 30, 1989,Attorney Agent, or F1'rmS. C. Yeaton; Howard P. has been disclaimedTerry [22] Filed: Apr. 20, 1973 [57] ABSTRACT [21] Appl' NOJ 353l56 Amethod for securing display anodes to related sup- Related US.Application Data port pins in a segmented planar raised unode fluores-[63] Continuation of Ser. No. 155956, June 25' 1971. cent Symbol p ytube employing a weld and abandonedt weld procedure.

[52] US. Cl 29/25.l6; 3l3/496 511 1111.01. HOlj 9/36 [58] Field 01Search 29/2513, 25.14. 25.15, 2 C'amm 6 Drawmg Flgures 29/2516; 3l3/lO8R, 109.5, 496

PATENTED 5l975 3,897, 614

.I/VVEIVTORS JAMES B. ARMSTRONG F|G.l.

A TTOR/VE) PATENTEDAUB 5197s 3. 8 97, 614 SHEET L l l y l INVENTORSJAMES E. ARMSTRONG METHOD FOR MANUFACTURING A SEGMENTED RAISED ANODEFLUORESCENT SYMBOL DISPLAY TUBE This is a continuation of applicationSer. No. 155,956 filed June 23, I971 abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates generally to a method of manufacturing a fluorescent symboldisplay tube and more particularly to a method for mounting the tubedisplay anodes on respective support pins.

2. Description of the Prior Art Known fluorescent tubes comprise asealed and evacuated envelope housing a supporting member containinganodes of luminescent material, and an electron emitter. The luminescentmaterial, such as phosphor, is deposited on the supporting member in thedesired anode configuration. Where a plurality of anodes are used, eachis physically separated from the others by a minimum distance so as tosimulate a continuity between adjacent excited anodes to provide avisually acceptable display. In compact small-sized tubes, the physicalseparation between the anodes is small resulting in a design which issusceptible to electrical leakage due to deposition of electricallyconducting particles between adjacent anodes. In some fluorescent tubedesigns, a mask is used to determine the configuration of each of theanodes, rather than shaping the anodes themselves in the desiredconfiguration. Such a design necessarily precludes continuity betweenthe adjacent excited anodes and may limit the viewing angle of thedisplay.

SUMMARY OF THE INVENTION The invention teaches a unique construction ofaplanar fluorescent indicator. The external envelope includes a substrateand a transparent portion or viewing window. A spacer, which may be anintegral part of the substrate or the transparent portion, is disposedtherebetween to define the envelope to be hermetically sealed. Thesubstrate includes a plurality of electrical conductors, or pins,extending therethrough. Each of a plurality of ribbonlike segments ofmetal having at least one surface coated with luminescent material is attached to the ends of a first set of pins extending into the envelopeand each forms an anode of the display. The resulting raised anodescooperatively provide the desired indicia, which may be of a segmentednumeric type. An electron emitter, such as a wire connected to a secondset of pins, is disposed within the envelope to provide the electronsource necessary to excite the luminescent material. The manner ofselectively exciting the anodes causing them to luminesce may be by anyof the well known electronic driving and switching means whereby theoutput of said means or circuitry is attached to the pins extending fromthe envelope and selectively energizes one or more of the leads for thedesired indicium, as well as energizing the electron emitter.

A primary object of the invention is to provide a thin planarfluorescent indicator.

Another object of the invention is to provide an increased surfaceelectrical path between adjacent fluorescent anodes.

Another object of the invention is to provide an effective heat sink forthe fluorescent anodes to dissipate the heat and thereby extend the lifeof the indicator.

Another object of the invention is to provide a fluorescent indicatorwith a large viewing angle.

Another object of the invention is to provide fluorescent anodes havingdirectly attached header pins.

Another object of the invention is to provide a simple inexpensivefluorescent tube structure which can be assembled by mass productiontechniques.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the basic elementsof a fluorescent display indicator;

FIG. 2 illustrates a cross-sectional view of the raised anode;

FIGS. 3a and 3b are schematic diagrams representative of the electricalcircuits;

FIG. 4 illustrates a modification of the electron emitter, and

FIG. 5 illustrates the tabs connecting each segment to a sheet; thefigure is substantially identical to FIG. I from U.S. Pat. No. 3,666,911incorporated by reference infra.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 there is shown anexploded view of the basic elements of the fluorescent tube 14comprising the invention, including a substrate 1, a plurality of anodesin the form of segments 2, an electron emitter 3, a spacer 4, and atransparent faceplate 5 for viewing the desired displayed indicium. Thecombination of substrate 1, spacer 4, and faceplate 5 form the enve lopeof the indicator. It is to be understood that either the substrate 1 orthe faceplate 5 may incorporate spacer 4 if desired. The substrate 1contains a plurality of conducting members 6, which may be metallicpins, that extend beyond the surface on either side of the substrate.The ends of the pins 6 extending beyond the outside of the envelope areconnected to driving circuitry (not shown) whereby voltage may beselectively applied to each of the anodes. The ends of the pins 6extending into the envelope have attached thereto me tallic ribbonlikesegments 2, generally having greater width than thickness. This ratiomay of course be modi fied depending on the type of indicium that is tobe displayed. Each of the pins 6 extends into the envelope a uniformdistance and each of the attached segments 2 are located in the samegeneral plane.

The means for attaching the segments 2 to the pins 6 may be by theprocess as described in a pending patent application entitled Method forManufacturing Planar Raised Cathode Gas Tubes," Ser. No. 5,436, filedJan. 23, 1970 and issued May 20, 1972, as US. Pat. No. 3,666,9II,assigned to the instant assignee. Briefly, in that process each of thesegments are formed in a metallic sheet and retained within the sheet byminute connecting tabs. The sheet is juxtaposed with the pins of thesubstrate such that the pins are aligned with the segments. Each segmentis welded to its respective pin by connecting the pin and the segment toa current source. After all welds are completed, current is applied toeach pin and the metallic sheet itself, whereby the current passingthrough the tabs will cause them to melt and free the segments from theretaining sheet. As each segment is severed, the current path becomesopen-circuited and the cessation of current flow provides a clearindication that the welding process has been completed.

The height of the segments 2 above the substrate 1 may be determined inany of several ways. The pins 6 may be formed as an integral part of thesubstrate 1 itself with one end flush with the surface of the substrateand the other end extending therefrom. The flush side is then etched topreferentially remove a portion of the substrate leaving the pins 6extending above the substrate 1. Another method may be that of insertingthe pins 6 into a plurality of holes in the substrate 1 and extending apredetermined distance from either side and sealing them thereto.

The segment side of each anode which faces toward the viewer is coatedwith a luminescent material, which may be a phosphor material (see FIG.2). The phosphor coating 7 may be of any of many known compositions andis selectable on the basis of its characteristics of persistence, color,brightness, efficiency, and its excitation voltage requirements. Thephosphor coating 7 may be applied to the sheet itself before or afterthe segments are identified, as manufacturing requirements dictate, orit may be applied to the segments 2 after they are attached to theirrespective pins 6. Dip coating or screen coating techniques areconsidered to be two feasible and satisfactory techniques for applyingthe phosphor coating. Scalable fill tube 8 is attached to the substrate1 and is used to evacuate the envelope.

ln previous fluorescent tubes, the phosphor coating was depositeddirectly on a base member located within an envelope. Any temperaturerise of one of the excited anodes resulted in transfer of heat to thebase member in addition to the heat absorbed from other thermal sourceswithin the envelope, specifically, the electron-emitting heatedfilament. Over a prolonged period, such a temperature rise has adetrimental effect on the base member and its phosphor coatings andreduced the effective life of the tube. The instant inventioncircumvents this deleterious effect as heat build-up in the phosphorbearing members is prevented by dissi pating the heat through the pins 6to the electrical terminals of the peripheral equipment. The attachmentof segments 2 directly onto external connecting pins 6 provides a heatsink very much superior to conventional practice where the thermal pathis degraded by an intermediate connecting wire and two welds. Theadditional length and generally smaller diameter of this connecting wireprovides a poor thermal path for dissipating heat into externalattachments to the leads. The technique of heat sinking in the subjectinvention per mits higher currents, and therefore increased brightnesswithout reducing the life of the tube.

Additional conducting members extend through the substrate and into theenvelope. These may also be pins 9 and form both thesupporting andenergizing means for the electron emitter 3. As with the pins 6 for theanodes 2, they are connected to appropriate driving cir cuitry toestablish a potential gradient between the electron emitter 3 and theanodes 2. In the simplest form, the electron emitter 3 is a wireextending across a portion of the substrate 1 and on the same side ofthe segments 2 as the phosphor coating 7. its exact length and locationin respect to the anodes 2 is dependent on the electrical and opticalrequirements of the indicator itself (principally uniformity) and may bedetermined empirically.

LII

As illustrated in FIG. 1 and described above, a fluorescent tube builtaccording to the teaching of the instant invention requires only simpleand straightforward assembly techniques. As such, the tube assemblyprocess is well suited to presently existing mass production techniques.

FIG. 2 illustrates a cross-sectional view of two adjacent anodes 2. Thepins 6 extend into and out of the envelope as described. The anodes 2attached to the pins 6 are raised above the substrate 1 as shown. Theeffect of raising the segments 2 substantially increases the surfacepath between the segments 2 to a substantially greater value than theactual least separation between segments. The increase in surfacedistance between the segments 2 tends to inhibit the formation of acontinuous surface electrical path from segment to segment and therebyreduces the probability of the anodes 2 shorting out.

In previous fluorescent displays, the base member supporting the anodeswas housed within an envelope, usually of a cylindrical shape. Such anenvelope dictated that the front to back tube dimension be no less thanthe width of the base member. When mounted in a display panel, thedisplay character in such a configuration is substantially recessed fromthe plane of the front of the panel, which severely limits the effectiveviewing angle. in the instant invention, the substrate 1 supporting theanodes 2 also forms a part of the envelope and thus eliminates the needfor a separate anode supporting member. With a reduction in the numberof required internal structural components, the volumetric andmanufacturing efficiency is increased. As the faceplate 5, or window, isplanar and parallel to the displayed character, it may be positionedparallel and very close to the anodes. Thus, the front to back distanceof the instant invention may be reduced to that of the thickness of thesubstrate 1, the faceplate 2, and the evacuated chamber containing theanodes 2. The close proximity of the displayed character to thefaceplate outer surface results in a substantial increase of the viewingangle over prior art devices.

A screen 10 shown in FIG. 1 may be placed between the electron emitter 3and the anodes 2 and energized through further conducting means, such aspins 13. The potential of the screen 10 must be positive with respect tothe electron emitter 3, and may be less than or equal to the potentialof the anodes 2, in order that is will attract and accelerate theemitted electrons toward the anodes 2. The addition of the screen 10 mayaid in dispersing the emitted electrons to more evenly distribute theelectron shower upon the anodes 2. As the phosphor coating 7 on theanodes 2 is luminescently responsive to the amount of excitation, aneven or near uniform electron shower will provide an essentially uniform visible response from all of the phosphor coated anodes 2.

FIG. 3a illustrates a schematic diagram for electrically connecting theelectron emitter 3 and the anodes 2, absent a screen 10. As shown, onepower supply 11 operates to heat the electron emitter 3 while the otherpower supply 12 establishes a potential gradient between the electronemitter 3 and anode 2 to direct the electrons toward the anodes 2. FIG.3b illustrates the modification necessary if a screen 10 is utilized. Ifthe screen 10 is at the potential of the anodes 2, the electrons whichdo not strike the screen 10, will continue on their trajectory andstrike the anodes 2, causing excitation of the phosphor coating 7. It isanticipated that there may be modifications of the circuits shown inFIGS. 3a and 3b to incorporate any one of known techniques to obtain auniform density of emitted electrons at the anodes 2.

FIG. 4 illustrates an end view of a modification in positioning theelectron emitter 3. ln applications where the height, that is, substrate1 to faceplate 5 distance, must be minimized, the electron emitter 3 maybe placed adjacent the substrate 1 and below the raised anodes 2. Wherethere is a danger of the heated electron emitter 3 cracking thesubstrate 1, it may be raised above the substrate 1 as shown. Inoperation, there may be an unequal degree of excitation of one portionof the phosphor coating 7 on one anode 2, or one or more anodes may bemore highly excited than other anodes, causing varying degrees ofluminescence. To overcome this variation, two or more physicallyseparated electron emitters 3 may be used to establish a more uniformelectron circuit across the phosphor coating 7 of each anode 2 and fromanode to anode. It is understood, of course, that a plurality ofelectron emitters may be utilized in the viewing side of the anodes 2 aswell.

While the invention has been described in its preferred embodiment, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from the true scopeand spirit of the invention in its broader aspects.

I claim:

1. A method for fabricating an anode array and base assembly of adisplay tube comprising the steps of providing a substantially planarnon-conductive tube base having electrically conductive anode supportpins passing in hermetically sealed relation through the base andextending upward from at least one surface thereof,

providing an electrically conductive sheet having anode segments formedtherein in a predetermined pattern and retained within the sheet by tabsconnecting each segment to the sheet,

juxtaposing the conductive sheet with the tube base so that each anodesegment is positioned adjacent an extending end of a mating anodesupport pin,

bonding each anode segment to a mating support pin to establish amechanically rigid electrical connection therebetween such that theanode segments will remain substantially in a common plane upon beingdisconnected from the electrically conductive sheet,

melting the tabs to sever the anode segments from the remaining portionof the conductive sheet. and

applying a luminescent coating to the side of the anode segments viewedin normal use of the tube after severing the anode segments from theremaining portion of the conductive sheet.

2. A method for fabricating an anode array and base assembly of adisplay tube comprising the steps of providing a substantially planarnon-conductive tube base having electrically conductive anode supportpins passing in hermetically sealed relation through the base andextending upward from at least one surface thereof,

providing an electrically conductive sheet having anode segments formedtherein in a predetermined pattern and retained within the sheet by tabsconnecting each segment to the sheet,

juxtaposing the conductive sheet with the tube base so that each anodesegment is positioned adjacent an extending end of a mating anodesupport pin,

bonding each anode segment to a mating support pin to establish amechanically rigid electrical connec tion therebetween such that theanode segments will remain substantially in a common plane upon beingdisconnected from the electrically conductive sheet,

melting the tabs to sever the anode segments from the remaining portionof the conductive sheet, and

applying a luminescent coating to the conductive sheet prior tojuxtaposing the sheet with the tube base so that the luminescent coatingon each anode segment is viewable during normal use of the tube.

1. A method for fabricating an anode array and base assembly of adisplay tube comprising the steps of providing a substantially planarnon-conductive tube base having electrically conductive anode supportpins passing in hermetically sealed relation through the base andexteNding upward from at least one surface thereof, providing anelectrically conductive sheet having anode segments formed therein in apredetermined pattern and retained within the sheet by tabs connectingeach segment to the sheet, juxtaposing the conductive sheet with thetube base so that each anode segment is positioned adjacent an extendingend of a mating anode support pin, bonding each anode segment to amating support pin to establish a mechanically rigid electricalconnection therebetween such that the anode segments will remainsubstantially in a common plane upon being disconnected from theelectrically conductive sheet, melting the tabs to sever the anodesegments from the remaining portion of the conductive sheet, andapplying a luminescent coating to the side of the anode segments viewedin normal use of the tube after severing the anode segments from theremaining portion of the conductive sheet.
 2. A method for fabricatingan anode array and base assembly of a display tube comprising the stepsof providing a substantially planar non-conductive tube base havingelectrically conductive anode support pins passing in hermeticallysealed relation through the base and extending upward from at least onesurface thereof, providing an electrically conductive sheet having anodesegments formed therein in a predetermined pattern and retained withinthe sheet by tabs connecting each segment to the sheet, juxtaposing theconductive sheet with the tube base so that each anode segment ispositioned adjacent an extending end of a mating anode support pin,bonding each anode segment to a mating support pin to establish amechanically rigid electrical connection therebetween such that theanode segments will remain substantially in a common plane upon beingdisconnected from the electrically conductive sheet, melting the tabs tosever the anode segments from the remaining portion of the conductivesheet, and applying a luminescent coating to the conductive sheet priorto juxtaposing the sheet with the tube base so that the luminescentcoating on each anode segment is viewable during normal use of the tube.